1. Field of the Invention
The present invention relates to a method and apparatus for image recording such as a copying machine, a facsimile and a printer. More specifically, the present invention relates to a method and apparatus for recording a prescribed image by emitting evaporated ink onto a recording medium.
2. Description of the Background Art
Conventional emitting type image recording apparatuses include ones employing ink jet method and ones employing electrostatic recording method. In the ink jet method, a liquid ink contained in a tank is pressurized by using a piezoelectric element or the like by an electric signal corresponding to image data, and the pressurized ink is emitted from a nozzle for printing. In the electrostatic recording method, powder or liquid (mist) ink is charged, the ink is drawn out from the nozzle by electrostatic attraction, and printing is done by opening/closing a shutter provided at a tip end of the nozzle by an electric signal corresponding to the image data. However, in the ink jet method, when air enters the ink tank, it becomes impossible to sufficiently pressurize the ink, so that printing fails. Further, this method suffers from clogging of the nozzle with ink and inferior image quality caused by bleeding of the ink on the recording medium, since liquid ink is used. The electrostatic recording method suffers from the problem of nozzle clogging when the ink is in the form of powder as the ink particles are caked by blocking. If the ink is liquid ink, this method also suffers from the problems of nozzle clogging and ink bleeding as in the ink jet method.
A method in which gaseous ink is emitted and adhere on a recording medium has been proposed as a method of solving the above described problems. In this method, nozzle clogging is less likely, since what is emitted is a gas. Further, since pixels are recorded by molecules, printing with higher resolution, high gradient and less ink bleeding is possible. This method is disclosed in Japanese Patent Publication No. 56-2020. The conventional image recording apparatus will be described in detail with reference to FIG. 14, which is a block diagram showing the structure of the conventional ink recording apparatus.
Referring to FIG. 14, the image recording apparatus includes a print head 101, a heating device 102, a charging electrode 103, electrostatic lenses 104, 105, an electrostatic shutter 106, a back plate 107, a power source 110 and a signal source 111. The heating device 102 includes a power source 108 and an electric heater 109.
Ink I1 in print head 1 is heated and evaporated by heating device 102 including electric heater 109 and power source 108. The evaporated gaseous ink Ig is shoot forth from print head 1. Gaseous ink Ig is charged by power source 110 inserted between charging electrode 103 and print head 101 when it passes through charging electrode 103 as it is shoot out. The charged gaseous ink Ig is focused by electrostatic lenses 104 and 105. Thereafter, the amount of emission of the focused gaseous ink Ig is controlled to be a prescribed amount, by electrostatic shutter 106 of which operation is controlled by signal source 111. The ink of which amount is thus controlled travels to back plate electrode 11, whereby an image is formed on a recording medium RM.
However, in the conventional image recording apparatus, the gaseous ink Ig is emitted continuously from print head 101, and the ink not actually used for recording is wasted, increasing running cost.